The instant invention generally relates to occupant detection systems for controlling the activation of vehicular safety restraint systems and more particularly for determining the presence and position of an occupant for purposes of influencing the deployment of safety restrain system responsive to a crash.
A vehicle may contain automatic safety restraint actuators that are activated responsive to a vehicle crash for purposes of mitigating occupant injury. Examples of such automatic safety restraint actuators include air bags, seat belt pretensioners, deployable roll bars, and deployable knee bolsters. One objective of an automatic restraint system is to mitigate occupant injury, thereby not causing more injury with the automatic restraint system than would be caused by the crash had the automatic restraint system not been activated. Generally, it is desirable to only activate automatic safety restraint actuators when needed to mitigate injury because of the expense of replacing the associated components of the safety restraint system, and because of the potential for such activations to harm occupants. This is particularly true of air bag restraint systems, wherein occupants too close to the air bag at the time of deploymentxe2x80x94i.e. out-of-position occupantsxe2x80x94are vulnerable to injury or death from the deploying air bag even when the associated vehicle crash is relatively mild. For example, unbelted occupants subjected to severe pre-impact braking are particularly vulnerable to being out-of-position at the time of deployment. Moreover, occupants who are of small stature or with weak constitution, such as children, small adults or people with frail bones are particularly vulnerable to injury induced by the air bag inflator. Furthermore, infants properly secured in a normally positioned rear facing infant seat (RFIS) in proximity to a front seat passenger-side air bag are also vulnerable to injury or death from the deploying air bag because of the close proximity of the infant seat""s rear surface to the air bag inflator module.
Air bags can be beneficial to any forward facing occupant when that occupant is a significant distance from the inflator door. Air bags, however, can be lethal to infants in rear facing infant seats (RFIS). Air bags can also be hazardous to forward facing occupants if they are too close to the inflator at the time of air bag deployment, such as when an unbelted occupant is subjected to severe pre-impact braking. Air bag inflators are designed with a given restraint capacity, as for example, the capacity to protect an unbelted normally seated fiftieth percentile occupant when subjected to a 30 MPH barrier equivalent crash, which results in associated energy and power levels which can be injurious to out-of-position occupants; to small or frail occupants such as children, small women, or elderly occupants; or to infants in rear facing infant seats (RFIS). While relatively infrequent, cases of injury or death caused by air bag inflators in crashes for which the occupants would have otherwise survived relatively unharmed have provided the impetus to reduce or eliminate the potential for air bag inflators to injure the occupants which they are intended to protect.
Automotive manufacturers and NHTSA are searching for methods to disable air bags in situations where they may cause more harm than good. Airbags have been developed to open with enough force to restrain a 175 lb. adult in a high velocity crash. When these air bags are deployed on children in the front passenger seat of a vehicle, they may cause serious injuries. Another potentially harmful situation is when the occupant is very close to the air bag inflator module at the time of air bag deployment. Recent NHTSA data suggests that severe injuries due to this close proximity with the inflator can be reduced or eliminated if the air bag is disabled when the occupant is closer than approximately four to ten inches from the inflator door. The region proximate to air bag inflator where the occupant could be at risk of injury from the air bag is called the xe2x80x9cat-riskxe2x80x9d zone. The size of the at-risk zone is dependent upon the inflation characteristics of the associated air bag inflator and the velocity of the occupant with respect to the air bag module. Previous studies had suggested that the at-risk zone extended out 4 to 10 inches from the inflator door, depending on the inflation module and the occupant size.
One technique for mitigating injury to occupants by the air bag inflator is to reduce the power and energy levels of the associated air bag inflator, for example by reducing the amount of gas generant in the air bag inflator, or the inflation rate thereof. This reduces the risk of harm to occupants by the air bag inflator while simultaneously reducing the restraint capacity of the air bag inflator, which places occupants at greater risk for injury when exposed to higher severity crashes.
Another technique for mitigating injury to occupants by the air bag inflator is to control the rate of inflation rate or the capacity of the inflator responsive to a measure of the severity of the crash. The prior art teaches the use of multi-stage inflators having distinct independent compartmentalized stages and corresponding firing circuits, whereby the stages may be fired in delayed succession to control the effective inflation rate, or stages may be inhibited from firing to control the effective inflator capacity. The prior art also teaches the use of a hybrid inflator having a combination of stored gas and plural pyrotechnic gas generator elements which are independently fired. Furthermore, the prior art also teaches the use of control valves for controlling the gaseous discharge flow from the inflator. The inflation rate and capacity may be controlled responsive to the sensed or estimated severity of the crash, whereby a low severity would require a lower inflation rate or inflation capacity than a high severity crash. Since lower severity crashes are more likely than those of higher severity, and since such a controlled inflator would likely be less aggressive under lower severity crash conditions than those of higher severity, occupants at risk of injury by the air bag inflator because of their size or position will be less likely to be injured overall because they are more likely to be exposed to a less aggressive inflator. However, the risk of injury to such occupants would not be mitigated under the conditions of higher crash severity when the inflator is intentionally made aggressive in order to provide sufficient restraint for normally positioned occupants.
Yet another technique for mitigating injury to occupants by the air bag inflator is to control the activation of the inflator responsive to the presence and position of the occupant, thereby activating the inflator only when an occupant is positioned outside the associated at-risk zone of the inflator. Recent NHTSA data suggests that severe injuries due to close proximity with the inflator can be reduced or eliminated if the air bag is disabled when the occupant is closer than approximately 4 to 10 inches from the inflator door. Such a system for disabling the air bag inflator requires a occupant sensor that is sufficiently sensitive and robust to make such a determination, while not causing the air bag inflator to be disabled when otherwise required for providing occupant restraint.
Except for some cases of oblique or side-impact crashes, it is generally desirable to not activate an automatic safety restraint actuator if an associated occupant is not present because of the otherwise unnecessary costs and inconveniences associated with the replacement of a deployed air bag inflation system. The prior art teaches various means for detecting the presence of an occupant, or the recognition of an inanimate object in the passenger-seat of a vehicle for purposes of implementing such a system. For example, weight sensors can incorporated into the seat to detect the presence of an occupant.
Yet another technique for mitigating injury to occupants by the air bag inflator is to control the inflation rate or inflation capacity of the air bag inflator responsive to presence and position of an occupant. Such a control system would most preferentially be used in conjunction with a controllable inflation system responsive to crash severity, such as described above, wherein the occupant position inputs can be used to override otherwise overly aggressive air bag inflator controls which might otherwise be indicated by the particular crash severity level but which could be injurious to occupants of small stature or weight, or to infants in rear facing infant seats. Such a system for controlling the air bag inflator requires an occupant position sensor that is robust and sufficiently accurate, and that can distinguish and discriminate various occupant scenarios and conditions.
The prior art teaches the use of sensors incorporated into the seat to detect the presence, weight, or seating position of the occupant. U.S. Pat. Nos. 3,672,699, 3,767,002, 5,161,820, 5,474,327, and 5,612,876 teach the use of occupant presence sensors incorporated into the seat to control the activation of the associated air bag inflator. U.S. Pat. No. 5,205,582 teaches a system for which the air bag inflator associated with an unoccupied seat is activated for accelerations above a second crash deceleration threshold, and otherwise deactivated. U.S. Pat. 5,074,583 teaches a plurality of sensors incorporated into the seat to detect occupant weight and seating position for purposes of controlling an air bag system. U.S. Pat. Nos. 5,232,243, 5,494,311, and 5,624,132 teaches an array of force sensing film elements incorporated into the seat for purposes of detecting the presence, weight, or position of an occupant for controlling either a multi-stage air bag inflator, an inflator vent valve, or the spatial orientation of the air bag inflator. U.S. Pat. No. 5,404,128 teaches the use of a vibration sensor incorporated into the seat to detect the subtle vibrations caused by the breathing and heart rhythms so as to determine whether or not a person is present. U.S. Pat. No. 5,573,269 teaches a means for correcting a seat weight measurement using seat back inclination angle and foot location. For some systems which incorporate seat weight as means for controlling the activation of an air bag inflator, the air bag inflator is required to be disabled if the sensed occupant weight is less than 30 Kg in order to assure that the air bag inflator is enabled for a fifth percentile female, but disabled for an infant in a rear facing infant seat. In some cases, as for example when the seat belt securing the infant seat is pulled too tight, an associated seat weight sensor could sense an apparent weight greater than the associated cut-off threshold so as to incorrectly enable the air bag inflator when a rear facing infant seat is present.
U.S. Pat. Nos. 5,071,160 and 5,118,134 teach the combination of sensing occupant position and/or velocity, and vehicle acceleration for purposes of controlling an inflator. Both of these patents teach by example the use of ultrasonic ranging to sense occupant position. U.S. Pat. No. 5,071,160 also teaches by example the use of a passive infrared occupant position sensor, while U.S. Pat. No. 5,118,134 teaches the use of a microwave sensor. U.S. Pat. No. 5,398,185 teaches the use of a plurality of occupant position sensors in a system for controlling safety restraint actuators in response thereto.
The prior art teaches the use of one or more ultrasonic beams reflected off the surface of an object to sense the location of the surface of the object. U.S. Pat. No. 5,330,226 teaches the combination of an ultrasonic ranging sensor mounted in the instrument panel and an overhead passive infrared sensor to sense occupant position for controlling a multi-stage air bag inflator or a vent valve connected thereto. U.S. Pat. Nos. 5,413,378, 5,439,249, and 5,626,359 teach ultrasonic sensors mounted in the dash and seat in combination with other seat sensors to detect the position and weight of the occupant for purposes of controlling an air bag inflator module. U.S. Pat. No. 5,482,314 teaches the combination of ultrasonic and passive infrared sensors together with associated signal processing for purposes of determining whether or not to deactivate a passive restraint system. U.S. Pat. Nos. 5,653,462 and 5,829,782 teach system for identifying and monitoring the contents of a passenger compartment by illuminating an object with a wave generator that directs waves towards the vehicle seat, and processing the received signal with a neural network or other pattern recognition system. Furthermore, U.S. Pat. No. 5,653,462 illustrates a system wherein the wave signal is first reflected off the windshield before reaching the vehicle seat.
The prior art also teaches the use of infrared beams reflected off the surface of an object to sense the location of the surface of the object. U.S. Pat. Nos. 5,446,661, and 5,490,069 teach an infrared beam directed by a transmitter at a point of reflection on the object. A receiver detects the radiation scattered from the point of reflection, and measures the distance of the point of reflection from the transmitter based upon a triangulation of the transmitted and received beams for purposes of controlling the activation of a safety restraint system. These patents also teach the combination of an infrared beam occupant position sensor with an acceleration sensor for purposes of controlling an air bag inflation system. U.S. Pat. No. 5,549,322 teaches the incorporation of a light beam occupant sensor into an air bag door. Furthermore, infrared beam sensors are commonly used as range-finders in automatic focusing cameras.
The prior art of U.S. Pat. Nos. 4,625,329, 5,528,698, and 5,531,472 teach the use of imaging systems to detect occupant position, the later two of which use this information for purposes of controlling an air bag inflator. U.S. Pat. Nos. 5,528,698, 5,454,591, 5,515,933, 5,570,903, and 5,618,056 teach various means of detecting the presence of a rear facing infant seat for purposes of disabling an associated air bag inflator.
The prior art also teaches the use of capacitive sensing to detect the presence, proximity, or position of an occupant. U.S. Pat. No. 3,740,567 teaches the use of electrodes incorporated into the base and back of the seat respectively, together with a capacitance responsive circuit, for purposes of discriminating between human occupants and animals or packages resting on an automobile seat. U.S. Pat. No. 3,898,472 teaches an occupant detection apparatus which includes a metallic electrode which is disposed to cooperate with the body of an automobile to form an occupant sensing capacitor, together with related circuitry which senses variations in the associated capacitance responsive to the presence of an occupant. U.S. Pat. No. 4,300,116 teaches the use of a capacitive sensor to detect people proximate the exterior of a vehicle. U.S. Pat. No. 4,796,013 teaches a capacitive occupancy detector wherein the capacitance is sensed between the base of the seat and the roof of the vehicle. U.S. Pat. No. 4,831,279 teaches a capacitance responsive control circuit for detecting transient capacitive changes related to the presence of a person. U.S. Pat. Nos. 4,9870,519 and 5,214,388 teach the use of an array of capacitive sensors for detecting the proximity of an object. U.S. Pat. No. 5,247,261 teaches the use of an electric field responsive sensor to measure the position of a point with respect to at least one axis. U.S. Pat. No. 5,411,289 teaches the use of a capacitive sensor incorporated into the back rest of the seat to detect occupant presence. U.S. Pat. No. 5,525,843 teaches the use of electrodes incorporated into the base and back of the seat for purpose of detecting the presence of an occupant, whereby the electrodes are substantially insulated from the vehicle chassis when the detection circuit is active. U.S. Pat. No. 5,602,734 teaches an array of electrodes mounted above the occupant for purposes of sensing occupant position based upon the influence of the occupant on the capacitance amongst the electrodes. U.S. Pat. No. 5,166,679 teaches a capacitive proximity sensor with a reflector driven at the same voltage as the sensing element to modify the sensing characteristic of the sensor. U.S. Pat. No. 5,770,997 teaches a capacitive vehicle occupant position sensing system wherein the sensor generates a reflected electric field for generating an output signal indicative of the presence of an object. U.S. Pat. Nos. 3,943,376, 3,898,472, 5,722,686, and 5,724,024 also teach capacitive-based systems for sensing occupants in motor vehicles.
The prior art teaches systemsxe2x80x94used alone or in combinationxe2x80x94for suppressing the passenger air bag in dangerous situations. These systems incorporate various sensing technologies, for example: active infra-red sensors; passive infra-red sensors (heat detectors); ultrasonic sensors; capacitive sensors; weight sensors (including various sensor technologies and measurement methods); child seat xe2x80x9ctagxe2x80x9d sensors; and vision-based systems.
An objective of these sensors is to determine when an occupant is very close to the inflator door and in the path of the deploying air bag, particularly out-of-position occupants and rear facing infants. Once detected, these systems need to employ the correct airbag deployment strategy such that the passenger side airbag is disabled when a rear facing infant seat is present, or when a person is within a specified region near the inflator door at the time a crash occurs. A complicating situation for the sensor is when there is an object, but no part of the occupant in the at-risk zone. Usually the air bag could still be beneficial for the occupant, especially if the object in the at-risk zone is a low density or low mass object like a newspaper or a map. Systems that only use ultrasonic and optical sensing mechanisms can be blocked by newspapers. Ultrasonic sensors in some configurations will be affected by environmental conditions (temperature, humidity, altitude) because the speed of sound changes depending on the environment. Any sensing system that needs a clear line of sight between the sensor and the occupant requires the sensor to be visible to the occupant.
Radar systems can be used to measure the range to an object; however, there is a perception that biological tissue may be adversely affected by the continuous exposure thereof to a radar beam. Notwithstanding that there is presently no evidence that a low power radar would have any biological effect, the perception issue is real, and accordingly it may be objectionable to have the radar continuously radiating within the interior of a vehicle interior. Usually two or more of these sensors are used together in an attempt to identify child seats, small occupants, empty seats, large occupants and out-of-position occupants. The more sensors that are used, the better the chance for a high performance system. The costs of systems that use many sensors, however, can become prohibitively high because of the large number of components and the increased assembly complexity of the vehicle.
Sensors which measure the distance between a point of reference and the surface of an object, such as ultrasonic or infrared beam sensors, are also vulnerable to false measurements, as would be caused for example by the presence of the extremities of an occupant, or by the presence of an object such as a scarf or newspaper held thereby, in proximity to the sensor. These types of sensors could be used to monitor the at-risk zone proximate the inflator door, but are subject to several disadvantages. In particular, infrared based systems usually incorporate a beam much narrower than the volume of the at-risk zone such that multiple beams may be required to reliably sense an object anywhere inside the at-risk zone. The incorporation of multiple beams results in extra cost, complexity, and potentially slowed response. Furthermore, both infrared beam and ultrasonic-based sensors would require a significant amount of hardware proximate the inflator door if the at-risk zone proximate the inflator is to be monitored.
One disadvantage of many occupant detection systems is that they do not gather the most relevant information to determine if the occupant is in an at-risk zone around the inflator module. Occupant detection systems that are mounted above the passenger and look down on the seat area have the wrong physical perspective to directly monitor the region around the inflator door. Even if an ideal set of roof mounted sensors can reliably determine the occupant""s gross positionxe2x80x94which is a very challenging task,xe2x80x94the actual volume between the inflator door and the occupant may be blocked to the sensors by the occupant""s body. If the criteria for controlling the activation of an air bag inflator were in part based on the proximity of the occupant""s body to the air bag inflator door, then overhead sensors simply cannot reliably obtain the relevant information. Systems that only use ultrasonic and optical sensing mechanisms can be blocked by newspapers. Ultrasonic sensors in some configurations will be affected by environmental conditions (temperature, humidity, altitude) because the speed of sound changes depending on the environment. Any sensing system that needs a clear line of sight between the sensor and the occupant requires the sensor to be visible to the occupant.
Some prior-art occupant detection systems attempt to identify the type of occupant or object in the passenger side seat, for example to discriminate a rear facing infant seat from a normally seated adult in the passenger seat. However, this is generally a very challenging task as there are a large variety of possible situations. Sensor systems that depend upon distance measurements to identify occupant situations generally use information from a relatively small number of points in space for identifying the particular type of occupant in the seat from amongst many possibilities. Results from these systems can be unreliable because a particular situation can be significantly changed by simple and common acts such as tossing a blanket over the occupant. Systems that can distinguish the occupant situation may be limited by the inability to disable the air bag during a pre-impact braking event. Moreover, the algorithms used in those systems are sometimes so complex that performance is sometimes unpredictable. While complex algorithms can sometimes makeup for the lack of direct sensory information, the same algorithms can sometimes create performance anomalies.
The instant invention overcomes the above-noted problems by providing a radar-based range finding system, the activation of which is responsive to a continuously active activation sensor, to suppress an air bag if an occupant is too close to the air bag inflator door after a vehicle crash has started. The continuously active activation sensor comprises either a crash sensor or a range/proximity occupant sensor, and the radar-based range finding system is in communication therewith. The instant invention detects a human body part that is within the at-risk zone of the air bag inflator at the time of impact such that the air bag can be disabled or its inflation rate can be reduced.
Air bags can be hazardous to forward facing occupants that are too close to the air bag inflator at the time of vehicle impact, as for example can occur when an unbelted occupant is exposed to severe pre-impact braking. To be effective, the sensor should detect the presence of the passenger near the air bag inflator within sufficient time so as to disable the air bag while the passenger is still xe2x80x9cflyingxe2x80x9d through the air during this pre-impact braking event.
The radar sensor incorporated in the instant invention is fast enough to identify an occupant""s position within several milliseconds. However, one disadvantage of a radar sensor to which occupants are exposed is the potential detrimental effectsxe2x80x94either real or perceivedxe2x80x94from exposure to the associated electromagnetic radiation. Consumers, and therefore automobile manufacturers, may hesitate to use a radar inside an automobile because of the perception of possible negative health effects, notwithstanding the lack of evidence that a low power radar would have any biological effect.
Accordingly, one object of the instant invention is to provide an improved occupant detection system, which when incorporated into an occupant restraint system, reduces the risk of injury to occupants by the associated air bag module.
A further object of the instant invention is to provide an improved occupant detection system that minimizes the exposure of an occupant to RF radiation.
A further object of the instant invention is to provide an improved occupant detection system that can determine if an occupant is positioned within the at-risk zone of the air bag module.
The instant invention provides for several methods and apparatus that could be used alone or together to allow the radar to be inactive until an object is in the at-risk zone or a vehicle is actually in a collision. The instant invention provides for fast communications and an activation feature that keeps the radar off until a signal from the crash sensing air bag control module is received, or until a range/proximity sensor detects an object in the at-risk zone. Upon activation of the radar incorporated in the instant invention, the system provides for disabling the air bag if the occupant is within the at-risk zone in front of the air bag inflator.
In accordance with another aspect, the radar doesn""t need to be active until an occupantxe2x80x94that when seated in a normal seating position in the passenger seat would require the deployment of an air bag responsive to a crashxe2x80x94is not seated in a normal seating position. A second occupant sensor, responsive to whether an occupant is in a normal seating position, also controls the activation of a radar for measuring occupant position, so that the radar is enabled to radiate energy only when the occupant is not in a position for which an air bag would be enabled. Stated in another way, the radar is prevented from radiating electromagnetic energy at a normally seated occupant detected by the second occupant sensor. The second occupant sensor identifies if an occupant is seated normally and thereby xe2x80x9cin-positionxe2x80x9d for a safe deployment of the air bag. If so, the radar is disabled. Otherwise, if an occupant is present, the radar is enabled.
In accordance with yet another aspect, when the second occupant sensorxe2x80x94adapted to detect a child seat or other xe2x80x9cstaticxe2x80x9d situation that may require that the air bag be disabledxe2x80x94detects a child seat, or any other xe2x80x9cstaticxe2x80x9d situation that may require that the air bag be disabled, the radar remains inactive and the airbag is suppressed. When the occupant is identified as being a normally seated occupant properly positioned to receive an air bag deployment, the radar is disabled and the air bag is enabled. The radar only becomes active when the normally seated occupant is no longer identified by the second occupant sensor as being properly positioned, i.e. xe2x80x9cin-positionxe2x80x9d. The radar is then used to identify whether the occupant is actually xe2x80x9cout-of-positionxe2x80x9d by sensing the at-risk region proximate to the air bag inflator module. Accordingly, most of the time the radar is off, thereby mitigating any real or perceived biological effects of the radar, but becomes activated, for example, when the occupant""s head or torso could be within the at-risk zone of the air bag inflation module. Moreover, this activation of the radar can be further limited to only when a crash sensor detects the potential for a crash of sufficient magnitude to possibly cause the deployment of the air bag inflator module.
The instant invention provides a number of associated advantages, including the following:
1. A radar can penetrate many materials. The depth of penetration depends on the material and the frequency of the radar.
2. The radar may sense a newspaper, but it can also sense objects beyond the newspaper.
3. The radar depends on the speed of light which does not vary significantly over automotive environments.
4. The radar is sufficiently fast to enable the control of a safety restraint system, because the associated range measuring process occurs at the speed of light, and the range data can be sampled at relatively high frequencies.
5. There are no moving parts in a radar.
6. The mechanism used in the radar is not sensitive to mechanical alignments, as are optical range finding systems that are calibrated based upon the mechanical position of associated imaging optics.
7. The radar can be hidden behind the trim pieces since it can transmit through thin sheets of plastic.
8. In one embodiment, because the activation of the radar is responsive to the crash in accordance with a communications path between the radar module and the frontal crash sensing unit, the radar remains inactive until a crash actually starts. Accordingly, there should be no threat, real or even perceived, of any biological effects due to the radar because the radar is inactive most of the time. For example, when activated responsive to a crash sensor, the radar doesn""t run until a crash actually begins. When it does run, the power density of the RF energy is well below conservative industry or government power density limits. The vehicle acceleration information can also be obtained by the radar module by using an on-board accelerometer, but preferably this information is relayed by high speed communications between the radar and the air bag control module, wherein the air bag control module controls when the air bags are deployed and accordingly knows when the occupant position measurement from the radar module is needed.
9. In another embodiment, the instant invention also provides for the combination of sensors to make an assessment of whether there is an occupant in the at-risk zone near the inflation module. A range/proximity sensor using ultrasonic, active IR, passive IR, capacitive sensing, vision, or inductive sensing technologies is used to constantly monitor the at-risk zone. When an object is detected within the at-risk zone by the range/proximity sensor, the radar is turned on to determine the type of object, for example such as a person, or a person holding a newspaper or map. The radar remains inactive until there is a possibility of the air bag inflator module deploying when there is an occupant in an at-risk zone of the air bag inflator module, and when activated, the radar detects the position of the occupant, and the actuation of the air bag inflator module is controlled responsive thereto.
10. The use of a radar along with a capacitive or inductive sensing technologies allows the system to robustly distinguish between newspapers and occupants in the at-risk zone.
11. In another aspect, the instant invention provides for controlling the air bag inflator module at least partially responsive to a second occupant sensor, wherein the radar remains inactive under conditions for which the second occupant sensor determines that either the air bag inflator module should be either disabled or enabled, and is activated when the second occupant sensor detects 1) an occupant that might require actuation of an air bag inflator module responsive to a crash, and 2) that the occupant is not normally seated so as to be at risk of injury by the deployment of the air bag inflator module. Accordingly, the second occupant sensor provides for further reducing the occupant""s cumulative exposure to the radar.
These and other objects, features, and advantages of the instant invention will be more fully understood after reading the following detailed description of the preferred embodiment with reference to the accompanying drawings and viewed in accordance with the appended claims.